<html>
<head>
<style>
#container {
    width: 300px;
}
#left {
    float: left;
    width: 100px;
    height: 100px;
    background: red;
}
#right {
    float: right;
    width: 100px;
    height: 150px;
    background: blue;
}
#clear1 {
    float: left;
    clear: left;
    width: 50px;
    height: 50px;
    background: green;
}
#clear2 {
    float: right;
    clear: right;
    width: 50px;
    height: 50px;
    background: green;
}
</style>
</head>
<body>
<div id="container">
<div id="left"></div>
<div id="right"></div>
<div id="clear1"></div>
<div id="clear2"></div>
</div>
</body>
</html>
